Sliding droplets of Xanthan solutions: a joint experimental and numerical study

TL;DR

This study combines experiments and simulations to analyze how non-Newtonian shear-thinning properties of Xanthan solutions affect droplet sliding behavior compared to Newtonian fluids, revealing the influence of rheological characteristics.

Contribution

It provides a quantitative comparison of droplet sliding for non-Newtonian Xanthan solutions and Newtonian fluids, introducing strategies to compute relevant dimensionless numbers for shear-thinning fluids.

Findings

Non-Newtonian behavior alters the relation between Capillary and Bond numbers.

Experimental and numerical results show shear-thinning impacts sliding velocity.

Methodology for computing the Capillary number in shear-thinning fluids is proposed.

Abstract

We have investigated the sliding of droplets made of solutions of Xanthan, a stiff rodlike polysaccharide exhibiting a non-newtonian behavior, notably characterized by a shear-rate dependence of the viscosity. These experimental results are quantitatively compared with those of newtonian fluids (water). The impact of the non-newtonian behavior on the sliding process was shown through the relation between the average dimensionless velocity (i.e. the Capillary number) and the dimensionless volume forces (i.e. the Bond number). To this aim, it is needed to define operative strategies to compute the Capillary number for the shear thinning fluids and compare with the corresponding newtonian case. Results from experiments were complemented with lattice Boltzmann numerical simulations of sliding droplets, aimed to disentangle the influence that non-newtonian flow properties have on the sliding.